Micro Adapative Flow Control
1.
2. Micro Adaptive Flow Control (MAFC) seeks to provide radical performance capabilities
in aircraft, engines, munitions, and maritime vehicle systems by controlling the behavior of
large scale flows by exploiting natural flow instabilities triggered by smaller scale
actuators.
By combining innovative actuator technologies with adaptive control strategies the program
will develop, assess, and demonstrate flow control approaches that may adaptively respond
to changes in operating conditions.
The key is to place the actuators where they will have the most effect. For example, small
actuator perturbations in the boundary layer at the leading edge of a wing can have dramatic
effects on the flow over that wing. The same actuators placed on the trailing edge will have
little to no effect.
3. The program will exploit recent developments in smart materials and MEMs
technologies together with innovative actuation concepts like synthetic jets to radically alter
flow behaviors.
Here we see how synthetic jets can radically change a bluff body separated to an attached
flow or even to a flow generating lift.
4. The MAFC Program has initiated multi-phased contracts to design, build, test, and
demonstrate the potential of various actuator concepts to control flows under realistic
conditions and to demonstrate their performance and effectiveness in selected military
systems applications.
5. Each contractor is required to define a system level military application, i.e.,
aerodynamics, gas turbines, munitions, or maritime systems.
The contractors will define an appropriate concept for flow control; design and develop the
capable actuators and controllers for the flow environment identified; and validate the
performance through testing.
And finally, the contractor must integrate them into a system that can be operated to
demonstrate systems performance and assure success in the chosen application.
6. BAA 98-19 released in February 1998 resulted in current contracts addressing three main
areas, as shown.
Another BAA is planned for the fall of 1999 that will call for ideas in the four broad areas:
aircraft, engines, munitions and maritime vehicles.
It is hoped that we will see a solid response especially in the areas of maritime applications
of flow control, as well as, applications to munitions.
The following three examples serve to illustrate MAFC concepts and challenges currently
being addressed.
We are interested in new and innovative ideas with the potential for radical performance
gains of similar magnitude to those illustrated in the examples.
7. Here is an example of MAFC applied to gas turbine compressors to prevent flow
separation on compressor blades.
If successful, this application of MAFC will allow replacement of several compressor blade
stages by a single high-work stage, greatly reducing cost and maintenance while increasing
thrust to weight and shortening the engine.
8. In this example, the downwash flow over the V-22 wing is controlled by MAFC to
produce a smaller separated flow region, reducing the downwash forces on the wing and
allowing a takeoff payload increase projected to be as large as 30 percent based on early
wind tunnel results.
9. In this last example, a small caliber munition is controlled using small actuators to steer
the projectile and guide it to a target, thereby more than doubling the range while improving
the accuracy, even in crosswinds.
In all three examples, a critical issue being addressed is the system level realizability of the
concept - meaning that the MAFC approach must make sense from a system-level
maintenance, robustness, and affordability standpoint.
10. DARPA will issue a BAA in the fall of this year.
Since the potential of adaptive flow control technology has not been fully explored, the
intent of the BAA will be to identify additional flow control actuators and systems concepts
with high payoff military systems applications.
Munitions, aerodynamic, engine, and maritime flow control will all be considered. There
will, however, be a special emphasis on the maritime systems applications.
DARPA is particularly interested in exploring and discussing the results of recent research
and changes in the state-of-the-art in flow control.
Information on innovative and advanced concepts, new approaches, and military
applications are of particular interest.